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Old 10-19-2014, 04:05 AM   #21 (permalink)
Human Environmentalist
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Join Date: Aug 2010
Location: Oregon
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Acura TSX - '06 Acura TSX
90 day: 24.19 mpg (US)

Lafawnda - '01 Honda CBR600 F4i
90 day: 47.32 mpg (US)

Big Yeller - '98 Dodge Ram 2500 base
90 day: 21.82 mpg (US)

Prius Plug-in - '12 Toyota Prius Plug-in
90 day: 57.64 mpg (US)

Mazda CX-5 - '17 Mazda CX-5 Touring
90 day: 23.6 mpg (US)

Chevy ZR-2 - '03 Chevrolet S10 ZR2
90 day: 17.14 mpg (US)
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Originally Posted by aerohead View Post
I pulled the belt off my CRX's alternator,ran out a tank,and couldn't perceive any mpg difference.I'm certain that it reduced the road load a bit,but not enough to show at the pump with crude testing.This was daylight-only driving with zero accessories on,just the ignition system running constant-loss off the battery.
Your vehicle may just have a very low electrical demand under the conditions you were running. As shown above, I have a base electrical demand of 14amps. The TSX has many electrical accessories, so it may be on the higher end of typical electrical usage.

The less electrical energy a vehicle uses, the less an alternator delete will improve fuel economy.

I would bet that if you normally drove at night, you would notice a higher mpg with an alternator delete.

Unfortunately, the more demand there is for electrical energy, and therefore potential for savings with an alternator delete, the larger and more costly the battery system must become.

Originally Posted by Cobb View Post
I thought maybe considering your location you found seat heaters was more efficient than running the hvac?
In my spreadsheet above, I show a base load of 14amps. Turning on the automatic HVAC adds 21amps, more than doubling and almost tripling the electrical load. A single seat heater adds 1 amp on low and 4 amps on high. To my surprise, it's much more efficient to generate heat by converting gasoline energy into mechanical energy, and then into electrical energy, and finally into seat heating, than to simply move the waste heat from the engine into the passenger compartment. It seems the reason for this is the cooling fan in the engine bay runs anytime the HVAC is engaged. On top of that is the blower motor, which I would assume still uses a power resistor to vary fan speed instead of PWM (more efficient).

I used to avoid the seat heaters, and instead wait for engine temps to come up before turning on the HVAC, but now I'll leave it off and instead run the seats, which have a very low impact on FE.

Originally Posted by Frank Lee View Post
Gonna go with a deep-cycle battery?
Probably 40 Ah LiFePO4, which it appears might cost as low as $200. My concern was the inability of charging this chemistry at anything below freezing, which happens about 2 months a year here.

My thinking is that it won't be a concern because I will run the engine before any need for charging will occur, and the engine bay temperatures will be significantly above freezing. If I need to engage the alternator on a longer trip, I simply drive until the need to engage, and then temperatures will have risen to acceptable levels. My normal routine will be to charge at home in the garage after having completed a trip. Again, engine bay temps will be above freezing.

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Last edited by redpoint5; 10-19-2014 at 03:36 PM..
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